Project on Logic gates

beenthere

Joined Apr 20, 2004
15,819
If you look at the spec sheet, you will notice that the maximum for Vcc for a TTL IC is 5.5 volts. The usual range is 4.5 - 5.0 volts. Applying 6 volts to pin 14 may have damaged the IC.

Your photo is too dark to make out the location of pin 1. Hopefully you have put ground and Vcc to the proper pins.

One further problem are the 6 inputs not connected. TTL IC's do not like this. The input voltage tends to rise to the operating point and cause oscillations. The result is a hot IC which is prone to malfunction. You should connect thise input pins to ground - the outputs may be left open.
 

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abhinavhardikar

Joined Aug 3, 2010
3
thank you very much! the PD is approx 5V because of high internal resistance! I checked it with a multimeter! Could someone tell me where I can find the internal circuit of the ICs?
 

JoeJester

Joined Apr 26, 2005
4,390
Assuming pin 1 is the closest we see in your picture.

You have gate 4's inputs floating. They can be low or high ... not floating. The same applies to any unused gates as well.

Your LED needs 150 ohm resistor to limit drop the difference between the output voltage, when it's high, and the 1.5V needed by the LED. A 150 ohm will suffice.

on edit ...

here is the schematic of one 7432 Or gate ... from the datasheet
 

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